It is well-known to digitize an audio signal and transmit the digitized audio signal in digital form. Such an audio signal will be reconverted to an analog form at a receiving location by means of a digital to analog converter. A typical method of digitizing an analog audio signal includes sampling an analog audio signal 8,000 times per second (8 Khz), each sample taking the form of an 8 bit byte. Such an audio sampling method produces a 64 kilobit per second data stream. At a receive location, such a 64 kilobit per second data stream is reconverted into an analog signal for use in an audio application.
For example, FIG. 1 shows an audio signal 102 which can be digitized by an analog to digital converter. As is well-known, samples such as samples 104, 106, 108 and 110 can be taken to periodically measure the amplitude of the signal. In the example of FIG. 1, for example, the sampling rate can be 8,000 times per second, such that the width of each of the samples 104-110 is one eight-thousandth of a second. Each of the samples 104-110 can be represented by an 8 bit word corresponding to the magnitude of audio signal 102 at the sampling time. Table 1 shows an example of representative values for samples 104-110.
TABLE 1 ______________________________________ Sample Va1ue Binary Value ______________________________________ 104 252 11111100 106 251 11111011 108 249 11111001 110 240 11110000 ______________________________________
These values, which correlate to a vertical scale of audio signal 102 in as manner known in the art, can then be transmitted as part of a bit stream representing the audio signal. For example, the pattern shown in FIG. 2 shows a portion of a bit stream corresponding to samples 104, 106, 108 and 110. In a conventional digital audio communication system, samples 104, 106, 108 and 110 are transmitted digitally to a destination system which converts the samples into an analog signal by way of a digital to analog converter.
It is also well known that a video image, such as a display on a television screen or on a computer monitor, is made up of a large number of picture elements (pixels). For example, a typical display in a personal computer system is made of a matrix of pixels, such as a 360.times.240 matrix having 240 rows and 360 columns. FIG. 3 shows a magnification of a portion of video display 301, which includes various pixels, such as pixels 303 and 305. In this example, designators 307, 309 and 311 refer to the first, second and third rows of pixels within display 301, respectively. Similarly, designators 313, 315 and 317 refer to the first, second and third columns of pixels within display 301, respectively.
As is known in the art, each pixel within display 301 can be illuminated to one of a plurality of intensities and can have one of a plurality of colors. By providing differing intensities and colors to the various pixels within display 301, a video image can be created on display 301.
Further, it is known that information regarding the color and intensity of a given pixel can be digitally encoded such that a digital bit stream can be configured to represent a specific image.
In a simplified example, suppose each pixel within image 301 can be illuminated at one of four intensities and can have one of four colors. For example, suppose pixel 303, and each of the other pixels within display 301, can have one of the following four intensities: very bright; bright; dull; and dark. Further, presume pixel 303 can be illuminated at a selected one of the aforementioned intensities and can take any one of the following colors: red; blue; green; and white. In this example, one can encode the information corresponding to a given intensity and a given color by using four bits of digital data. For this simplified example, this concept can be seen by reviewing FIGS. 4A-4C. Here, FIG. 4A shows that each of the potential intensity levels can be characterized by two bits. FIG. 4B shows that each of the potential colors can similarly be characterized by two bits. FIG. 4C shows, for a subset of the possible combinations of intensities and colors from FIGS. 4A and 4B, that four bits of information can characterize a given state of a pixel. For example, if a pixel is to be illuminated to a very bright red state, the corresponding information is represented by 1111. Similarly, if a given pixel is to be illuminated to a bright blue state, the corresponding information can be represented by the digital sequence 1010.
Presuming that pixel 303 (FIG. 3) is to be illuminated to a very bright red state, and that pixel 305 is to be illuminated to a bright red state, a portion of a digital bit stream as shown in FIG. 5 can represent the information corresponding to the desired state of these two pixels. For example, segment 503 corresponds to the 1111 characterization of a very bright red pixel, and segment 505 corresponds to the 1011 bit representation for a bright red pixel. Regarding segment 505, one can see that since the bit stream is traveling in the direction of the arrow in FIG. 5, the highest order bit, which is in the first place of the segment, is at the rightmost portion of the segment. This is purely by way of example and not of limitation. If the sending and receiving devices operate under a different protocol, the leftmost bit of a segment can correspond to the highest order of the segment.
As described above, it is known to digitally encode information corresponding to the desired intensity and color of each pixel within a display such that, when this information is processed, the pixels of the display can be individually illuminated according to the corresponding portion of the information in order to produce a meaningful display. Also, as shown in FIG. 5, it is conventional to transmit the digital information corresponding to the pixels of a display in a predefined sequence in order to limit the amount of bits within the bit stream which must be allocated to overhead functions. In the example shown in FIG. 5, the information for pixel 303 is immediately followed by information from pixel 305. Thus, there is no need to provide extensive overhead to identify which pixel corresponds to the given information. Instead, a protocol is established which sets out a specific sequence of pixel information so that a display processor can process the information in order to create the display based on the information.
The example shown in FIGS. 4A-4C and 5 is an extremely simplified example merely for purposes for illustration. In modern digital video processing applications, a significantly greater number of bits are used to characterize each pixel's projected state. For example, 16-bit video is widely used, although new and future applications use 32-bit video. In these applications, the intensity and color of each pixel can take one of a great number of states. As a result, the image presented on the video display can be life-like, and even three-dimensional in quality.